Aroma Stability of Lemon-Flavored Hard Iced Tea Assessed by Chirality and Aroma Extract Dilution Analysis

Unraveling the contribution of aroma-active and chiral compounds to different grade of Yashi Xiang teas using stir bar sorptive extraction

Yashi Xiang (YSX) is a flavor of Fenghuang Dancong tea and famous for its name and floral aroma, which is a type of semi-fermented oolong tea. However, previous research into the aroma characteristics of YSX tea mostly focused on the aroma compounds, and little research on chiral compounds in YSX has been performed. Therefore, the current study was conducted to explore the aroma characteristics of YSX tea from the perspective of enantiomers of chiral compounds. A total of 12 enantiomers were determined in this study, among them, (R)-(-)-α-ionone, (S)-(+)-linalool, (1S,2S)-(+)-methyl jasmonate, (S)-z-nerolidol, (R)-(+)-limonene, and (S)-(-)-limonene have important effects on the aroma components of YSX tea. The ER ratios of the enantiomers were different in samples of different grades. Therefore, this parameter can be used to identify the grade and authenticity of YSX tea. PRACTICAL APPLICATION: The study illuminates the aroma characteristics of YSX tea from the perspective of enantiomers of chiral compounds, which have important effects on the aroma components of YSX tea. It established an ER ratio system to effectively distinguish the grade and authenticity of YSX tea by comparing the ER of YSX tea. Focusing on analyzing the chiral compounds in the aroma of YSX tea is helpful in providing a theoretical basis for the authenticity of the precious tea and improving of the quality of YSX tea products.

Understanding of formation and change of chiral aroma compounds from tea leaf to tea cup provides essential information for tea quality improvement

Abundant secondary metabolites endow tea with unique quality characteristics, among which aroma is the core component of tea quality. The ratio of chiral isomers of aroma compounds greatly affects the flavor of tea leaves. In this paper, we review the progress of research on chiral aroma compounds in tea. With the well-established GC-MS methods, the formation of, and changes in, the chiral configuration of tea aroma compounds during the whole cycle of tea leaves from the plant to the tea cup has been studied in detail. The ratio of aroma chiral isomers varies among different tea varieties and finished teas. Enzymatic reactions involving tea aroma synthases and glycoside hydrolases participate the formation of aroma compound chiral isomers during tea tree growth and tea processing. Non-enzymatic reactions including environmental factors such as high temperature and microbial fermentation involve in the change of aroma compound chiral isomers during tea processing and storage. In the future, it will be interesting to determine how changes in the proportions of chiral isomers of aroma compounds affect the environmental adaptability of tea trees; and to determine how to improve tea flavor by modifying processing methods or targeting specific genes to alter the ratio of chiral isomers of aroma compounds.

Aromatic Profiles and Enantiomeric Distributions of Chiral Volatile Compounds in Pu-Erh Tea

Pu-Erh tea, as a typical post-fermented tea, can be divided into raw Pu-Erh tea (RAPT) and ripened Pu-Erh tea (RIPT) according to the processing technology. It is famous for its unique aroma after aging. Although previous research on the aroma characteristics of Pu-Erh tea mostly focused on the aroma compounds, little research on chiral compounds in RAPT and RIPT has been performed. Therefore, the current work aims to explore the aroma characteristics of Pu-Erh tea from the perspective of enantiomers of chiral compounds. A total of 15 enantiomers were determined in this study, among which (R)-(-)-2,2,6-trimethylcyclohexanone, (R)-(-)-linalool, (S)-(+)-linalool, (R)-(+)-δ-octanolactone, (R)-(+)-γ-nonanolactone, (2R,5R)-(+)-theaspirone A, and (R)-(-)-dihydroactinidiolide were identified as enantiomeric compounds that play an important role in the aroma of RAPT and RIPT. Furthermore, (2S,5R)-trans-linalool oxide and (R)-(+)-α-terpineol were important contributors to the aroma profile of RAPT, while (S)-(+)-2-methylbutanal, (S)-(-)-limonene, S-(-)-α-terpineol, and (1R,2R)-(-)-methyl jasmonate contributed to the characteristic aroma of RIPT. The addition of these enantiomeric compounds brings the aroma closer to that of the original tea sample. In addition, the analysis of chiral enantiomers of linalool, limonene, theaspirone A, and γ-nonanolactone can provide guidance for the quality and flavor control of Pu-Erh tea aroma.

Microbial Communities and Flavor Compounds during the Fermentation of Traditional Hong Qu Glutinous Rice Wine

As a traditional Chinese rice wine, Hong Qu glutinous rice wine (HQW) is popular among consumers due to its unique flavor. However, its quality changes during fermentation, and the potential relationships between flavor and microbes have not been systematically researched. In this work, physicochemical properties (pH, total sugar, alcohol, amino acid nitrogen), flavor compounds (organic acids, free amino acids, and volatile compounds), and microbial communities were investigated. The results revealed that Pantoea, Lactiplantibacillus, Lactobacillus, Leuconostoc, and Weissella predominated the bacterial genera, and Monascus was the predominant fungal genus. Organic acids, free amino acids, and key volatile compounds (esters and alcohols) significantly increased during fermentation. The correlations analysis showed that Lactiplantibacillus was closely associated with flavor compounds formation. This study deepens our understanding of the roles of microorganisms in flavor formation on traditional HQW fermentation.

Occurrence of Marine Ingredients in Fragrance: Update on the State of Knowledge

The fragrance field of perfumes has attracted considerable scientific, industrial, cultural, and civilizational interest. The marine odor is characterized by the specific smell of sea breeze, seashore, algae, and oyster, among others. Marine odor is a more recent fragrance and is considered as one of the green and modern fragrances. The smells reproducing the marine environment are described due to their content of Calone 1951 (7-methyl-2H-1,5-benzodioxepin-3(4H)-one), which is a synthetic compound. In addition to the synthetic group of benzodioxepanes, such as Calone 51 and its derivatives, three other groups of chemical compounds seem to represent the marine smell. The first group includes the polyunsaturated cyclic ((+)-Dictyopterene A) and acyclic (giffordene) hydrocarbons, acting as pheromones. The second group corresponds to polyunsaturated aldehydes, such as the (Z,Z)-3,6-nonadienal, (E,Z)-2,6-nonadienal, which are most likely derived from the degradation of polyunsaturated fatty acids. The third group is represented by small molecules such as sulfur compounds and halogenated phenols which are regarded as the main flavor compounds of many types of seafood. This review exposes, most notably, the knowledge state on the occurrence of marine ingredients in fragrance. We also provide a detailed discussion on several aspects of essential oils, which are the most natural ingredients from various marine sources used in fragrance and cosmetics, including synthetic and natural marine ingredients.

Volatile Profile Characterization of Winter Jujube from Different Regions via HS-SPME-GC/MS and GC-IMS

A combined untargeted and targeted approach was established for fingerprinting volatile organic compounds in winter jujubes from eight regions of China. Volatiles, including alcohols, aldehydes, acids, esters, and alkenes, were identified by gas chromatography-ion mobility spectrometry (GC-IMS). Benzyl alcohol, octanoic acid, 2-hexenal, linalool, 2-nonenal, and ethyl decanoate were the most common compounds present in all jujubes. Principal component analysis (PCA) from GC-IMS and untargeted E-nose showed that the main volatile organic compounds (VOCs) of most jujubes were similar. The volatile organic compounds of winter jujubes from Yuncheng city, Shanxi province, and Aksu region, Xinjiang province, were significantly different from those from other regions. 1-Penten-3-ol, ethyl hexanoate, methyl laurate, and 2-formyltoluene were the markers of XJAKS with green and fruity aroma, and SXYC could be labeled by acetone and 2-methoxyphenol with woody and pungent aroma. GC-IMS was an effective method for volatile fingerprinting of jujubes with high sensitivity and accuracy.

Effects of Storage Conditions on the Flavor Stability of Fried Pepper (Zanthoxylum bungeanum) Oil

Flavor stability of fried pepper oil was investigated during 30 days of storage. Variation trends of key volatile flavor compounds in fried pepper oil induced by ultraviolet (UV) irradiation and oxygen (O2) exposure were compared using GC-MS and chiral GC-MS analysis. Chirality analysis showed that conversion of (S)-(-)-limonene to (R)-(+)-limonene form was observed during storage. The storage conditions did not change the configuration of linalool, linalool oxide, or carvone. Quantitative analysis showed that the concentrations of linalool, limonene, 1,8-cineole, β-myrcene, and β-ocimene decreased dramatically during storage, whereas carvone, (E)-2-heptenal, and linalool oxide showed an increasing trend during storage. The loss rate of limonene and linalool exhibited the highest under combined UV and O2 condition, which played an important role for the aroma attenuation of pepper oil. This result will benefit the storage of pepper oil and based on pepper oil aromatic products.

Characterization of key aroma compounds and enantiomer distribution in Longjing tea

By comparing the enantiomers of authentic Longjing tea, the authenticity of Longjing tea can be effectively distinguished. In this study, 18 enantiomers were identified using a chiral column. At the same time, the unique enantiomer ratio (ER) of Longjing tea (LG1, LG2, LG3, LG4, LG5) of different grades and origins was determined. The ER can provide a theoretical basis for distinguishing Longjing tea of different grades and origins, and for identifying the authenticity of Longjing tea. The ER ratio of (R)-(-)-1-octen-3-ol and (S)-(+)-1-octen-3-ol can be used to identify LG1 (71:29). The ER ratio of (S)-(+)-α-ionone and (R)-(-)-α-ionone can be used to identify LG2 (65:35). The ER ratio of (R)-(-)-dihydroactinidiolide to (S)-(+)-dihydroactinidiolide (71:29) can also be used to detect LG3. The ER ratio of (R)-(+)-Limonene and (S)-(-)-limonene can be used to identify LG4 (20:80). The ER ratio of (R)-(-)-linalool to (S)-(+)-linalool (12:83) was available to identify LG5.

Characterization of Key Odorants in Hanyuan and Hancheng Fried Pepper (Zanthoxylum bungeanum) Oil

Fried pepper (Zanthoxylum bungeanum Maxim.) oil has been widely used in traditional Chinese cuisine and has recently become increasingly popular in food manufacturing. Thus, the aroma profiles of Hancheng pepper oil (HCPO) and Hanyuan pepper oil (HYPO) from two regions were investigated by aroma extract dilution analysis (AEDA) combined with gas chromatography-mass spectrometry-olfactometry (GC-MS-O). Results from AEDA showed that more aroma compounds with flavor dilution factors ≥9 were detected in HCPO than in HYPO. The odor activity values (OAVs) revealed 28 odorants with OAVs ≥1 in HCPO or HYPO. High OAVs were in particular obtained for 1,8-cineole, (E)-2-heptenal, β-myrcene, β-ocimene, limonene, and linalool. Then, the aroma profiles of HCPO and HYPO were successfully simulated through aroma recombination models. Omission tests suggested that β-phellandrene, p-cymene, acetic acid octyl ester, octanal, citronellol, and sabinene played key roles in aroma differences between HCPO and HYPO. In addition, varying enantiomeric ratios of linalool (floral) and limonene (citrus-like and lemon-like) in HCPO and HYPO were observed by chiral GC-MS, and the odor impressions of limonene and linalool were in good agreement with the odor descriptions of S-(-)-limonene and S-(+)-linalool.

Characterization of Jinhua ham aroma profiles in specific to aging time by gas chromatography-ion mobility spectrometry (GC-IMS)

A rapid method for analyzing of Jinhua ham samples in different aging time was created based on gas chromatography-ion mobility spectrometry (GC-IMS). The GC-IMS chromatograph provided information regarding the identities and intensities of 37 volatile flavor compounds, including both monomers and dimers. Principal component analysis (PCA) effectively distinguished the variation in the aroma of the Jinhua hams specific to aging time. Alcohol (octanol, 2-methylbutanol), ketones (2-butanone, 2-hexanone, 2-heptanone, acetoin, gamma-butyrolactone), aldehydes (butanal, 3-methylbutanal), ester (propyl acetate) and carboxylic acids (3-methylbutanoic acid) were considered as the main volatile compounds in the Jinhua ham samples. This GC-IMS method, then, proved to be feasible for the rapid and comprehensive detection of volatile compounds in Jinhua hams, and multivariance analysis (i.e.: PCA) was able to provide information related to aging time.

The Blossoming of Technology for the Analysis of Complex Aroma Bouquets-A Review on Flavour and Odorant Multidimensional and Comprehensive Gas Chromatography Applications

Multidimensional approaches in gas chromatography have been established as potent tools to (almost) attain fully resolved analyses. Flavours and odours are important application fields for these techniques since they include complex matrices, and are of interest for both scientific study and to consumers. This article is a review of the main research studies in the above theme, discussing the achievements and challenges that demonstrate a maturing of analytical separation technology.

Effects of Different Fermentation Strains on the Flavor Characteristics of Fermented Soybean Curd

The effects of different fermentation strains on the flavor characteristics of fermented soybean curd (FSC) were investigated in this study. Fresh tofu was fermented by Actinomucor elegans, Rhizopus arrhizus, Mucor racemosus, and Rhizopus chinensis, either alone or in various combinations. The FSC manufacturing process included prefermentation by different strains at 28 °C for 60 hr, followed by salting at 16 °C for 7 days and finally proceeding postfermentation at 25 °C for 35 days. Subsequently, five tested samples were obtained, namely, sample A (fermented by A. elegans alone), R (fermented by R. arrhizus alone), AR (fermented by A. elegans and R. arrhizus at 5:1), AM (fermented by A. elegans and M. racemosus at 1:1), and RR (fermented by R. arrhizus and R. chinensis at 7:3). The flavors of the five samples were determined by E-nose, sensory evaluation, and GC-MS. E-nose system observed significant discriminations by principal component analysis and linear discriminant analysis analysis. Sensory evaluation ranked the overall sensory scores: AR>AM>A>RR>R. As shown in GC-MS results, sample AR also had, on average, the highest level of many volatiles. Out of 10 critical volatiles, the detected frequency of samples AR, AM, RR, A, and R was 10, 9, 9, 8, and 7, respectively. PLS2 regression model was used to explore the influence on flavor quality of different strains. All three analytic methods revealed similar results, with sample AR providing the best flavor quality, while the opposite was the case with sample R. Therefore, it could be concluded that A. elegans and R. arrhizus at 5:1 (v/v) was the optimal combination, and may likely promote the production of critical volatile compounds. PRACTICAL APPLICATION: The flavors of fermented soybean curds are influenced by various factors such as physicochemical and microorganism during the fermentation surroundings. The results of this work not only provide valuable information for FSC flavor studies, but can also guide the FSC industry to improve flavor quality by applying the most appropriate production strains.